I’m in the process of transferring from a different host that uses CPanel. Cpanel has a mechanism that is supposed to archive the site (databases, mail, everything) and transfer it via FTP, but that didn’t work, so I instead am manually FTP’ing the tar.gz file it created over to my DH server. This is going to take about 6 hours though, given the 1/2 gig file size. I’m surprised it’s that slow, given that both servers are have fast connections, so I’m wondering whether there is a better way to do this.

Bit late now but maybe wget would have been quicker.
SSH to your DreamHost account and run wget from there. You would then use DreamHosts fat pipes!
You might have had to ince username/password in the wget commandline. man:wget